Charcoal adsorbent test apparatus and method using filter tubes

ABSTRACT

An apparatus and method for testing the performance of a sample charcoal  orbent material. The apparatus comprises means for supplying a gaseous sample containing toxic contaminants to a filtering means. The filtering means includes a filter tube containing a sample charcoal adsorbent material for adsorbing the toxic contaminants. Chemical analysis means are included for detecting toxic contaminants remaining in the gaseous effluent from the filtering means. Test animal chambers are also provided for exposing test animals contained therein to the gaseous effluent to determine the toxic effects and breathing rate changes on the test animals caused by toxic or irritating contaminants remaining in the gaseous effluent.

The invention described herein may be manufactured, used and licensed byor for the Government for Governmental purposes without the payment tous of any royalties thereon.

FIELD OF THE INVENTION

The present invention relates to an apparatus and a method forevaluating the performance of a sample charcoal adsorbent material. Moreparticularly, the present invention relates to an apparatus and methodfor testing the ability of a sample charcoal adsorbent material toremove toxic contaminants from a gaseous sample.

BACKGROUND OF THE INVENTION

Charcoal adsorbent materials are well known in the art for removingindividual components from gaseous or liquid mixtures. Charcoaladsorbent materials are used in many industrial applications for suchseparation purposes. Charcoal adsorbent materials are also used inprotective gas mask devices in order to provide a safe source ofuncontaminated air for breathing in a contaminated environment. In thefield of protective gas masks, however, it has been difficult todetermine under realistic test conditions how well various types ofcharcoal adsorbent materials protect against different types ofcontaminated or toxic gases.

More particularly, the testing of charcoal filter cartridges orcanisters included in protective gas masks requires large quantities oftest gases and extended analysis time in order to determine theperformance of a particular sample charcoal adsorbent material.Additionally, chemical analysis performed on the effluent from thefilter cartridges or canisters does not always detect the presence oftoxic materials. Similarly, such chemical analysis may indicate thepresence of a compound of unknown toxicity. Moreover, to be usedeffectively as a filter material in a protective gas mask, charcoaladsorbent materials must protect against highly irritating vapors, forexample, vapors which irritate eyes, skin and respiratory systems.Chemical analysis of filter effluents may not detect the presence ofsuch irritating materials or may indicate the presence of compoundswhose highly irritating properties are not known. Thus, chemicalanalysis alone often provides an incorrect estimate of the performanceand effectiveness of a charcoal adsorbent material for use in aprotective gas mask. Accordingly, there is a need for an apparatus andmethod for quickly and effectively evaluating the performance of variouscharcoal adsorbent materials.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodand apparatus for quickly and effectively evaluating the performance ofa sample charcoal adsorbent material.

It is a further object of the invention to provide an apparatus andmethod for quickly and effectively testing the performance of a samplecharcoal material particularly adapted for use in a protective gas mask.

It is a related object to provide an apparatus and method for testingthe performance of a sample charcoal adsorbent material by detecting thepresence of toxic contaminants remaining in the gaseous effluent from afilter containing the charcoal adsorbent material and by determining thetoxicity and irritating properties of the gaseous effluent from thefilter containing the charcoal adsorbent material.

It is also an object of the invention to provide a method for testingthe performance of a sample charcoal adsorbent material which employssmaller quantities of sample gases than known methods and which requiresreduced analysis time as compared with known methods.

These and other objects and advantages are provided by the apparatus andmethod of the present invention. The apparatus comprises means forsupplying a gaseous sample containing toxic or harmful contaminants to afiltering means. The filtering means includes a filter tube havingsmaller dimensions than the filter canisters or cartridges used inprotective gas masks. The filter tube contains a sample charcoaladsorbent material for adsorbing the toxic contaminants contained in thegaseous sample. Chemical analysis means are included for detecting toxiccontaminants remaining in the gaseous effluent from the filtering means.Test animal chambers are also provided for exposing test animalscontained therein to the gaseous effluent in order to determine thetoxic effects and irritating properties of the gaseous effluent.

In accordance with the method of the present invention, a gaseous samplecontaining toxic or harmful contaminants is supplied to a filteringmeans where the gaseous sample is passed through a filter tubecontaining a sample charcoal adsorbent material. The gaseous effluentfrom the filtering means is forwarded to a chemical analyzer tochemically analyze and detect any toxic contaminants remaining in thegaseous effluent and test animals are exposed to the gaseous effluent inan enclosed area to determine the toxic effects and irritatingproperties of any toxic contaminants remaining in the gaseous effluenton the test animals.

Additional objects and advantages of the apparatus and method accordingto the present invention will become apparent from the followingdetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWING

The detailed description of the apparatus and method of the presentinvention will be more completely understood when viewed in connectionwith the drawings in which:

FIG. 1 is a schematic diagram of a first embodiment of the apparatus ofthe invention;

FIG. 2 is a schematic diagram of a second embodiment of the apparatus ofthe invention;

FIG. 3 is a cross sectional view of a preferred filtering means includedin the apparatus of the invention;

FIGS. 4 and 5 are graphical representations of measured respiratorychanges in test animals in an apparatus of the invention and employingthe method of the invention; and

FIG. 6 is a graphical representation of the amounts of unabsorbed toxiccontaminants from two different types of charcoal adsorbent materials atdifferent humidities employed in the method and apparatus of theinvention, wherein the concentration of contaminants in the filtereffluent, in ppm, is plotted as a function of time, in minutes.

DETAILED DESCRIPTION

The present invention thus relates to an apparatus and method forevaluating the performance of a sample charcoal adsorbent material. Theapparatus and method are particularly adapted for testing theeffectiveness and performance of a sample charcoal adsorbent material inseparating particular components from a gaseous sample. In this regard,the apparatus and method are valuable for determining the suitability ofvarious charcoal adsorbent materials for use in protective gas masks.

Generally, the apparatus of the invention includes a supply means forsupplying a gaseous sample containing harmful or toxic contaminants to afiltering means for removing the toxic contaminants from the gaseoussample. The filtering means includes a filter tube containing a samplecharcoal adsorbent material which adsorbs the toxic contaminantsthereon. The apparatus further includes chemical analysis means forchemically analyzing the gaseous effluent from the filtering means inorder to detect any toxic contaminants remaining in the gaseouseffluent. Additionally, test animal chambers are included in theapparatus for exposing test animals contained therein to the gaseouseffluent from the filtering means in order to determine the toxiceffects on the test animals of any toxic contaminants remaining in thegaseous effluent. The test animal chambers specifically include meansfor measuring respiratory changes in the test animals in order todetermine any irritating effects of the gaseous effluent on therespiratory systems of the test animals.

A first embodiment of the apparatus in accordance with the presentinvention is set forth in FIG. 1. The supply means for supplying agaseous sample containing toxic contaminants as set forth in FIG. 1comprises a gas cylinder 1 containing the test gas and a gas cylinderregulator 2. The test gas containing harmful or toxic contaminantspasses through a mass flow controller 3 which controls the amount oftest gas which is metered into the testing system. In a preferredembodiment, a temperature-flow-humidity controller 4 is provided in theapparatus for conditioning dilution air which may be mixed with the testgas to the desired temperature, flow and relative humidity. Bycontrolling the temperature, flow and humidity of the dilution air, thetemperature, flow and humidity of the gaseous sample which is forwardedto the filtering means may also be controlled.

Flow control means are provided, for example, four-way ball valves 5 and6, for directing the gaseous sample to and from the filtering means. Thefiltering means 7 is disclosed in more detail in FIG. 3, and comprises afilter tube 7a having an inlet 7b for receiving a gaseous samplecontaining toxic contaminants and an outlet 7c for delivering a filteredgaseous effluent. The filter tube 7a may conveniently comprise a filtertube made of glass or other chemically inert material. The filter tubecontains a sample of charcoal adsorbent material 7d. The charcoaladsorbent material is retained within the filter tube by means of aporous member 7e comprising, for example, a stainless steel screen. Aglass cylinder or other block material 7f is provided in the lowerportion of the filter tube in order to provide a supporting platform forthe adsorbent material. In a preferred embodiment, filter tube 7a is ofa reduced size as compared with filter canisters and cartridges used inprotective gas masks and preferably has a length of about 6 to 12inches.

Proper control of four-way ball valve 6 allows a gaseous sample to beforwarded to the filtering means 7 as shown by arrow A and gaseouseffluent to be directed from the filtering means 7 to the chemicalanalyzer 8 as shown by arrow B. Chemical analyzer 8 analyzes the gaseouseffluent from the filtering means to detect toxic contaminants remainingin the gaseous effluent. In a preferred embodiment, only a portion ofthe gaseous effluent from the filtering means is directed to thechemical analyzer 8 and the remaining portion of the gaseous effluent isforwarded to the test animal chambers 9 and 10. The chemical analyzermay comprise any means well known in the art for detecting components ofa gaseous sample. For example, the chemical analyzer 8 may comprise aninfra-red spectrometer.

The apparatus further includes test animal chambers 9 and 10 forexposing test animals contained therein to the gaseous effluent from thefiltering means 7. The test animals are exposed to the gaseous effluentin order to determine any toxic or irritating effects on the testanimals of any toxic contaminants remaining in the gaseous effluent. Thetest animal chambers also include means for measuring any respiratorychanges in the test animals, which indicate irritation of therespiratory systems of the animals by the gaseous effluent. In apreferred embodiment, the means for measuring respiratory changescomprise plethysmographic boxes 14 and 15 included in the test animalchambers 9 and 10, respectively. Test animals such as mice and rats areuseful in the apparatus of the invention.

A second embodiment of the apparatus according to the present inventionis set forth in FIG. 2 in which members corresponding to those set forthin FIG. 1 are given the same reference numerals. The embodiment of FIG.2 differs from that of FIG. 1 in that the gaseous sample supply meansincludes means for vaporizing a liquid sample. Specifically, a syringepump 11 is provided for metering a predetermined amount of a vaporizableliquid and forwarding the liquid sample to a mixing T-connector 12.T-connector 12 is included for mixing the liquid sample with apredetermined amount of dilution air from the flow-temperature-humiditycontroller 4. The air-liquid sample mixture is then forwarded tosuitable means for vaporizing the liquid, which means 13 is disclosed inFIG. 2 as a vaporizing coil. The vaporizing means 13 ensures that theliquid sample is adequately vaporized to provide a gaseous sample beforeforwarding the same to the filtering means 7.

The apparatus of the invention, particularly as set forth in FIGS. 1 and2, may conveniently be used in a method for testing the effectivenessand performance of a sample charcoal adsorbent material in accordancewith the present invention. More particularly, the method of theinvention comprises the steps of supplying a gaseous sample containingtoxic contaminants to a filtering means including a filter tubecontaining a sample charcoal adsorbent material therein, passing thegaseous sample through the filtering means to remove the toxiccontaminants from the gaseous sample, forwarding the gaseous effluentfrom the filtering means to a chemical analyzer to chemically analyzeand detect any toxic contaminants remaining in the gaseous effluent andfinally exposing test animals to the gaseous effluent from the filteringmeans in an enclosed area in order to determine the toxic effects on thetest animals of any toxic contaminants remaining in the gaseouseffluent.

The method of the invention may further include the preliminary step ofvaporizing a liquid sample containing toxic contaminants in order toprovide a gaseous sample containing toxic contaminants. Moreover, therespiratory response of the test animals to the gaseous effluent may bemeasured, for example by use of plethysmographic means.

Thus, the apparatus and method of the invention provide a convenientsystem for testing the effectiveness and performance of a samplecharcoal adsorbent material in separating specific components, forexample toxic contaminants, from a gaseous sample. Various charcoaladsorbent materials for use, for example, in protective gas masks may berapidly tested using small amounts of test gas samples. Chemicalanalysis of the filter effluent provides detection of various toxiccontaminants remaining in the gaseous effluent and the exposure of testanimals to the gaseous effluent provides an indication of the toxiceffects of any contaminants remaining in the gaseous effluent. Apreferred method employing the apparatus of the invention is set forthbelow.

With reference to FIG. 1, the apparatus and method of the presentinvention are employed to evaluate the performance of a sample charcoaladsorbent material. A sample of a charcoal adsorbent material isinserted in the glass filter tube 7 which is then connected with theremainder of the apparatus as set forth in FIG. 1. The four-way valve 5is adjusted to a purge position to admit purge air and the four-wayvalve 6 is positioned to allow the purge air to pass in the direction ofarrow A into the filtering means and in the direction of arrow B out ofthe filtering means. Purge air is admitted to the system to purge thecharcoal adsorbent material in the filter tube of any residualcontaminants prior to testing. Purge air is also forwarded to thechemical analyzer 8, for example an infrared spectrometer, so that aninitial instrumental baseline may be established. Test animals areplaced in the respective test inhalation chambers and allowed toacclimate to the experimental surroundings so that a baselinerespiration rate may also be recorded.

Once the system has been purged and the analyzer and respirationbaselines have been established, the four-way valve 5 is positioned toclose the purge air inlet and to receive a gaseous sample for deliveringto the downstream four-way valve 6. The temperature-flow-humiditycontroller 4 is activated to condition air to the desired temperatureand humidity and control the flow rate of the conditioned air. The testgas cylinder regulator 2 is opened and a sample test gas is metered fromthe cylinder 1 by adjusting the mass flow controller 3. If a vaporizableliquid sample is to be used, the syringe pump 11 in conjunction with theT-connector 12 is used to meter the test sample into the conditioned airstream. The liquid sample-air mixture is then vaporized at vaporizingmeans 13 to provide a gaseous sample.

The gaseous sample is then forwarded through four-way valves 5 and 6 tothe filtering means 7 containing the charcoal adsorbent material. As thegaseous sample passes through the charcoal adsorbent material, toxiccontaminants contained in the gaseous sample are adsorbed onto thecharcoal material. At least a portion of the gaseous effluent isforwarded to the chemical analyzer 8 while the remainder of the gaseouseffluent is forwarded to the test animal chambers 9 and 10 in order toexpose the test animals to the gaseous effluent. This operation iscontinued for a sufficient period of time, for example 30 minutes,during which time the respiratory responses of the test animals aremonitored, for example using plethysmographic means. The filter effluentis also monitored using the chemical analyzer.

After the challenge period, the supply of the gaseous sample isdiscontinued and the system is purged for an additional time period, forexample 30 minutes, in order that any reversibly bound componentsadsorbed on the charcoal material may be desorbed. The animals areremoved from the test chambers and are observed for toxic signs for anextended period, for example one week or more.

The charcoal adsorbent material contained in the filter tube 7 may beeasily exchanged with other charcoal adsorbent materials in order todetermine the effectiveness and performance of the various charcoalmaterials.

Two tests were performed in accordance with the method and apparatus ofthe present invention using two different types of charcoal adsorbentmaterials, respectively. FIGS. 4 and 5 set forth results of therespiratory response of test animals from the two tests run inaccordance with the apparatus and method of the present invention. Alltests represented by FIGS. 4 and 5 were conducted at a temperature of25° C., a flow rate of 5.2 lpm and a relative humidity less than 15%. Inboth FIGS. 4 and 5, curves A and B represent the breathing rate of ratsand mice, respectively, in relation to exposure time. FIG. 4 indicatesthat in the first test, using a first type of charcoal adsorbentmaterial, there were minimal changes in the breathing rates of rats andmice when exposed to a gaseous effluent from the filtering meanscontaining the first charcoal adsorbent material for a period of thirtyminutes. Specifically, the mice evidenced little or no irritation,whereas the rats evidenced a mild irritation near the end of the thirtyminute exposure period. A 100% survival rate for both rats and miceresulted, four of each rats and mice being used. Thus, the charcoaladsorbent material was effective under the conditions of this test.

In contrast, the results of FIG. 5 indicate that there were significantchanges in the breathing rates of both rats and mice during the secondtest when exposed to the gaseous effluent from the filtering meanscontaining a second type of charcoal adsorbent material. The data setforth in FIG. 5 suggests that an irritant, anesthetic or asphyxiant waspresent in the effluent from the filtering means. A 100% rat survivalrate resulted, 4 of 4 survived, while a 50% mice survival rate resulted,2 of 4 survived. Therefore, it is concluded that the second charcoaladsorbent material used in the second test was not protective under thetest conditions.

The temperature, flow rate and humidity of the gaseous sample which issupplied to the filtering means affects the performance of the charcoaladsorbent material contained therein. For example, additional tests wereperformed using two gaseous samples, respectively, which were identicalexcept for the relative humidity of the gaseous samples. Results ofthese tests are set forth in FIG. 6, which discloses the concentrationof contaminants not adsorbed on two types of charcoal adsorbent materialin PPM versus the time of exposure of the charcoal material to thegaseous samples. Both the challenge period wherein the charcoal materialis exposed to the gaseous sample and the purge period where the charcoalmaterial is purged of any reversibly bound contaminants are set forth inFIG. 6. The measured concentration of contaminants on the differenttypes of charcoal material, A and B, are represented in FIG. 6 bytriangles and circles, respectively. Tests were performed at 15%relative humidity and 80% relative humidity and the results in FIG. 6are so indicated. It is observed from FIG. 6 that both charcoalmaterials were less effective at the higher relative humidityconditions.

Thus, the apparatus and method of the present invention provide for therapid and effective testing of the performance of various samplecharcoal adsorbent materials under various test conditions.

The advantages and embodiments set forth herein are illustrative onlyand are not intended to limit the scope of the present invention.Additional embodiments and advantages within the scope of the presentinvention will be apparent to those of ordinary skill in the art.

What is claimed is:
 1. An apparatus for testing the performance of asample charcoal adsorbent material, comprising(a) means for supplying agaseous sample containing contaminants to a filtering means; (b)filtering means for removing the toxic contaminants from the gaseoussample, said filtering means including a filter tube containing a samplecharcoal adsorbent material for adsorbing thereon the toxiccontaminants; (c) chemical analysis means for chemically analyzing thegaseous effluent from the filtering means to detect toxic contaminantsremaining in the gaseous effluent; and (d) test animal chambers forexposing test animals contained therein to the gaseous effluent fromsaid filtering means to determine the toxic effects on the test animalsof toxic contaminants remaining in the gaseous effluent, said testanimal chambers including means for measuring respiratory changes in thetest animals.
 2. An apparatus as defined by claim 1, wherein saidgaseous sample supply means includes means for controlling thetemperature, humidity and flow rate of the gaseous sample.
 3. Anapparatus as defined by claim 1, wherein said gaseous sample supplymeans includes means for vaporizing a liquid sample.
 4. An apparatus asdefined by claim 1, wherein said chemical analysis means comprises aninfra-red spectrometer or other suitable analytical detector.
 5. Anapparatus as defined by claim 1, wherein said filter tube comprises aglass tube and has a length of about 6 to 12 inches.
 6. An apparatus asdefined by claim 1, wherein said means for measuring respiratory changesin the test animals comprises plethysmographic means.
 7. A method fortesting the performance of a sample charcoal adsorbent material,comprising(a) supplying a gaseous sample containing toxic contaminantsto a filtering means; (b) passing the gaseous sample through a filteringmeans including a filter tube containing a sample charcoal adsorbentmaterial therein to remove the toxic contaminants from the gaseoussample; (c) forwarding the gaseous effluent from the filtering means toa chemical analyzer to chemically analyze and detect toxic contaminantsremaining in the gaseous effluent; and (d) exposing test animals to thegaseous effluent from the filtering means in an enclosed area todetermine the toxic effects on the test animals of toxic contaminantsremaining in the gaseous effluent.
 8. A method as defined by claim 7,including the preliminary step of vaporizing a liquid sample containingtoxic contaminants to provide a gaseous sample containing toxiccontaminants.
 9. A method as defined by claim 7, wherein the gaseouseffluent is chemically analyzed using an infra-red spectrometer or otherappropriate analytical detector.
 10. A method as defined by claim 7,including the step of controlling the temperature, humidity and flowrate of the gaseous sample.
 11. A method as defined by claim 7,including the further step of measuring the respiratory response of thetest animals to the gaseous effluent.
 12. A method as defined by claim11, wherein the respiratory response of the test animals is measuredusing plethysmographic means.
 13. An apparatus as defined by claim 1,wherein said chemical analysis means comprises an analytical detector.14. A method as defined by claim 7, wherein the gaseous effluent ischemically analyzed using an analytical detector.